Split-field dual-power telescope



L. G. HENYEY ETAL SPLIT-FIELD DUAL-POWER TELESCOPE Filed May 25, 1947 WW a en 1 mwz mm M T E Q MW. a

Jane 20, 1950 Patented June 20 1950 STATES PATENT OFF ICE SPLIT- FIELDDUAL-POWER TELESCOPE- I-iouis GM Henyey' and Jesse L. Greenstein,Williams Bay, Wis.,. assignorsetovthe United, States of America asrepresented-by theSecretary of War Application-May23, 1947, Serial No.749,970

4 Claims. (CI. 8832) v This inyentionyrelates to a, splitefleld,dualpower telescopewhich, while,..oi general utility, iaparticularlyuseiul in. combat tanks and other armored vehicles. is well, known, the.vision from the interior of a tank is extremely limited because.onthenecessity for. protectionto the operatingrpersonneln This =condition.oi limited vision israggravatcdyby the restrictedspace within thetank:turret... v In.the;case; oi carrying relativel-yrlargeO8.lib16!g;uIlS, :the, gunner. vhas numerouadutiestdpertorminiadditiontothose customanilyaperformed..bymthe, gunner oi anemplaced gun;-t Eor; example, -thegunner-mustordinaai1y-seleet-a.i'-targe judge {the .ran r, tr t theirgnndqader as ttype, oflammunition, watch theetarget movement tocorrectrfon lead andma: nipulatetheccntrols allundenthestressoibattle Iandintaerampedpositionwithin;thevehicle.

1 Underithe foregoing conditionsit is-a greataid to rthe gunner.tozhaveeavailable two. closely adj aent.images creche?and;the?samefield of: view, andfat different magnifications.-- The, field of. viewoi-zlowen magnifioation yin-covering. a larger area;

enables inspection overr'anrelativelywide area and telescope embodying:the" invention; the tube,

mounting; andzjotherewell-known details being omittedforrsimplicity'iof:illustrationand description u a Figure 2 israviewishowingfthevmanner' otprodueingvthe upper eccentric. collectivelens,

figurefi is'a views shew-ingthemannenofproducingthelmivm? eccentriccollective-lens; and

T Figure yisva typiealrview of anzenemy tanlt at 2 two differentmagnifications, as it appears in the fielder the telescope. I

The lower objective is a telephoto lens of. 10.6" focallength consistingof a pair of doublets I, 2

i and 3, 4. The collective 5 is a semi-circular eccentric=lens cut asshown at Figure 3,;Ircm a large ordinary circular. lens and having itsflat edge in the horizontal plane through the central axis of theinstrument.

The upper objective is an inverted telephoto lens of 3.l8"focal length,consisting ofthe doublets l5, l6 and H, L These particular objectivesare required to make it unnecessary for the objective of longer focus toproject an excessive distance in front of the other. The eccentriccollective i9 is cut from an ordinary lens, as shown in Figure 2. Toprevent light from one objective from passing to the wrong collectiveand producing false images; the two objectives are separated withintheir common tube, by a thin metal vane 20. This appears asadiametralline 29', Figure 4. In the absence of specially-cut collectives5 and. IS, the entrance pupi-lswould be imaged at different pointsbehind the eyepiece and both would be displaced off'the main opticalaxis 2|. By the use of the collectives, cut as shown at Figures 23 and-3 to have a prismatic action, the entrance pupils arefocussed to producea single round Ramsden disk behind the eyepiece. In the model shown, theoptical axes of the objectives are displaced\0.55" above and below axis2|, respectively. Lenses 5 and I9 may be molded in plastic and cut froman ordinary lens 246 in diameter by a straight chordalcut ofiset 0.55"from their center, and: a semi-circular cut centered on the midpoint ofthe chord.

The second collective lens 6. is a single element extending over bothobjectives. This lens may have a flat rear face and is designed to befree of significant aberrations. The'rear vertex. of lensfi lies in thesame transversesplane as the front of lens 6. Theirontfacesof lenses5and it are coplanar and, since these two are of differentthickness, asshown in the accompanying table, the plane of the vertexof [9 lies".014" forwardly. ofthe plane of the vertex oflens 6;- Bythisarrangement', the two reticles maybe boresightedwith respect to eachother at'the factory and. one boresighting in the field properly adjustsboth... Reticles of any suitable type and of desired form; may beprovided, as by etching, upon the fiatfaces ofv these lenses.

The 'erector consists of the two doublets I, 8 and 9; HL Of conventional'form, designed to be free r-significant; aberrations. A diaphragm 22;of

Thus, at a single round exit pupil the observer it sees two images of atarget as shown at Figure 4. 3

In the lower half of the eyepiece he is able to obtain a view over arelatively wide field. In the model selected for illustration, the fieldof view of the wide angle side, with a 1.5:: magnification,

is 40 wide and'20 high. In the upper half, a

magnification of 5X is provided with a field 12 wide and 6 high. -Nochange of eyepiece, or motion of the observers head is required to shiftfrom one magnification to the other; and no light is lost by splittingthe entrance rays into two parts. In short, the invention is theequivalent of two telescopes with the added advantage of elimination ofmotion of the observers head. The definition of the image is of highquality over both fields.

The following table gives the actual values used in the modelillustrated, the lens number corresponding in each instance with thenumbers used upon Figure 1.

[All dimensions in inches] Separation Lens Radii tum cases a s s W sNNNNFi-i-EN esssssseseeec 9999????". momcweurm u sO tOOwWNO c0000We'have thus provided a telescope that is relatively simple andinexpensive to produce in quantities. At the same time the instrument iscompact and can be built to withstand the shocks, jars, and roughhandling incident to service in the field.

In order fully to comply with the requirements of the patent statutes,we have disclosed a specific form of the invention. However it will beobvious to those skilled in the art that different absolute and relativemagnifications may be employed and that the fields of view may be variedas to absolute and relative areas. Furthermore, substitutions ofequivalents and changes in the relations of the parts will occur'tothose skilled in the art after a study of the present disclosure. Forexample, the: two areas of different magnifications may be separated ina horizontal direction or in any other direction relative to thehorizontal or the vertical, merely by arranging the conventional rangereticles on the fiat surfaces of elements 5 and [9, so that they will heVertical 4 I and horizontal when the telescope is in the desiredposition of rotation about its optical axis. In the absence of suchreticles, of course, or where their use is not required, the desiredposition of rotation may be obtained simply by mounting the telescope inits support for rotation about its optical axis. Also, the line ofseparation between the two fields may be displaced from the diametralposition to give any .10..

desired ratio between the areas of the two apparent fields. For thesereasons, the disclosure should be taken in an illustrative rather than alimiting sense; and it is our desire to reserve all .suchchanges as fallwithin the scope of the subjoined claims.

In the claims, the term "eccentricity as re- 'ferred toeccentric-collective lenses 5 and I 9,

means the distance between the optical axis of the spherical lens fromwhich the eccentric lens was out, and the geometrical center of theeccentric lens. Thus, in the model shown, lenses 5 and I9 have aneccentricity of 0.55".

.Ha'vingthus fully disclosed our invention, what we claim and desire tosecure by Letters Patent 1s:

1. In a split-field dual-power telescope having a central optical axis,a first objective comprising a first telephoto lens in normal positionand having its principal axis offset a predetermined. distance from andparallel with, said central axis, a second objective comprising a secondtelephoto lens in inverted position and of lesser focal length than saidfirst lens, said second lens having its principal axis offset by saidpredetermined distance from said central axis, said two principal axesforming diametrically opposite elements of a cylinder having its axis onsaid central optical axis, a first semi-circular eccentric collectorlens optically centered on the principal axis of said first objective, asecond semi-circular eccentric collector lens optically centered on theprincipal axis of said second objective, said collector lenses having aneccentricity equal to the radius of said cylinder and having their'diametral edges contiguous and their forward faces coplanar, a thirdcollector lens adjacent and extending over both said first and secondcollector lenses, erector lens means and an eyepiece both having theirprincipal ax es coincident with said central optical axis, saidcollector lenses bringing to a common focus the entrance pupils ofdiscrete difierently magnified images of a common field of viewprojected by said objectives and centered on said central optical axis,and an opaque vane in said telescope on said central axis and extendingbetween said objectives and first'and second collector lenses.

2. In a split-field, dual-power telescope having a principal opticalaxis, first and second objectives of different focal lengths havingtheir central axes parallel with and offset on respective diametricallyopposite sides of said principal optical axis, said first and secondobjectives being separate telephoto lenses in-side-by-side parallelrelation, one said telephoto lens being inverted with respectto theother to project at different magnifications, discrete images of thesame remote field of view, a single eyepiece centered on said principalaxis rearwardly of said objectives. and optical means comprising firstand second prismatic collective lenses lying in a common lane acrosssaid principal axis between said objectives and eyepiece,each saidcollective lenses being constructed and arranged to direct the entrancepupil of'a respective objective into said eyepiece to form a single exitpupil rearwardly thereof.

3. In a dual-power, split-field telescope having a central longitudinalaxis, a first objective having its principal axis parallel with saidcentral axis and offset therefrom a predetermined distance, a secondobjective having its principal axis parallel with said central axis andoffset therefrom on the side opposite the principal axis of said firstobjective,all said axes lying in a common plane, said objectives beingseparate telephoto lenses lying in side-by-side relation, one saidtelephoto lens being inverted with respect to the other, a commonerector lens and an eyepiece for both said objectives, and centered onsaid central axis, first and second coplanar semicircular prismaticcollector lenses mounted with their diameters in contact between saidobjectives and said eyepiece, each said collector lens having aneccentricity equal to said predetermined distance and constructed andarranged in conjunction with said erector lens and eyepiece, to focusthe entrance pupil of its objective to a single exit pupil rearwardly ofsaid eyepiece.

4. In a dual-power, split-field telescope having a central longitudinalaxis, first and second objectives of difierent focal lengths in fixedadjacent side-by-side relation with their respective optical axesparallel to and equally spaced on opposite sides of said central axis,said objectives comprising separate telephoto lenses one of which isinverted with respect to the other, an eyepiece having its principal axicoincident with said central axis, and a collective lens comprisingfirst and second semi-circular eccentric lenses in a common planebetween said objectives and eyepiece, said collective lenses each havingan eccentricity equal to the spacing of each said optical axis from saidcentral axis and having their diametral edges contiguous, saidcollective lenses focusing together in a common plane through the focalpoint of said eyepiece, the entrance pupils of said objectives, wherebyan observer at said eyepiece may see in the exit pupil, discrete imagesof a common field of view at different magnifications.

LOUIS G. I-IENYEY.

JESSE L. GREENSTEIN'.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 578,459 Leuner Mar. 9, 1897841,262 Martin Jan. 15, 1907 1,094,724 Konig Apr. 28, 1914 1,290,777OBrien Jan. 7, 1919 1,840,931 Bjorn Jan. 12, 1932 1,986,731 KollmorgenJan. 1, 1935 2,388,673 Brown Nov. 13, 1945 2,409,186 Bouwers Oct. 15,1946 FOREIGN PATENTS Number Country Date 15,123 Great Britain of 19111,727 Great Britain Nov. 18, 1915 312,317 Germany Oct. 18, 1921

